Both the Warrior Dash (that I did) and the toughmudder are held at ski resorts in Ontario, meaning you're climbing up and down the mountain throughout the course. I consider myself athletic and I workout religiously - The obstacles are fun and in the case of Warrior, they're the easiest part... still, you can't help but get winded running under the blazing heat of the sun up and down the mountain. It's a challenge for sure